The energy problems have been discussed frequently in recent years. To meet the increasing energy demands around the world and to reduce energy consumption, more and more researches and developments are focusing on renewable energy. Solar energy is one of the best alternative as it is capable of producing a large amount of energy while meeting the requirement of environment protection.
Despite its great potential, one major limitation of solar energy is that in order for it to function, a solar-powered device needs to be exposed to solar radiation. Yet many devices used in the environment of our daily life, especially in-doors, are rarely, if ever, exposed to solar radiation directly. So the solar energy that can be converted into electric energy is limited. This is one of that reasons why solar energy device cannot be used conveniently and widely in every environment.
Especially in reference to illuminating devices such as lights and lamps used at night for every family, or signs and the like used at night, it would highly desirable if they can be charged by solar energy. However, currently available devices need to be taken outdoors during the day for charging and indoors where they are used. A need exists for improvements that would free the users from such cumbersome practice.